Bifunctional air electrode

• US 20070166602A1
• Filed: 12/06/2006
• Published: 07/19/2007
• Est. Priority Date: 12/06/2005
• Status: Abandoned Application

• Current Assignee: Revol Technologies Inc.
• Original Assignee: Revol Technologies Inc.
• Inventors: Burchardt, Trygve
• Application Number:
  US11/634,379
• Publication Number:
  US 20070166602A1
• Time in Patent Office: Days
• US Class Current: 429/406
• CPC Class Codes: H01M 12/08 composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type
• CPC Class Codes: H01M 4/0435 Rolling or calendering
• CPC Class Codes: H01M 4/8652 as mixture
• CPC Class Codes: H01M 4/8875 Methods for shaping the electrode into free-standing bodies, like sheets, films or grids, e.g. moulding, hot-pressing, casting without support, extrusion without support
• CPC Class Codes: H01M 4/8896 Pressing, rolling, calendering membrane electrode assemblies H01M8/1004
• CPC Class Codes: H01M 4/9016 Oxides, hydroxides or oxygenated metallic salts
• CPC Class Codes: H01M 4/92 Metals of platinum group H01M4/94 , H01M4/9058 take precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Air electrodes for secondary metal-air batteries or secondary metal hydride-air batteries, in particular, bifunctional air electrodes that can undergo oxygen reduction and oxygen evolution with high reaction rates. A method of manufacturing such electrodes.

Claims

1. A bifunctional air electrode for a secondary metal-air battery comprising a gas diffusion layer, an active layer, an oxygen evolution layer and a current collector in electrical contact with the active layer;

wherein the active layer contains an oxygen reduction catalyst and a bifunctional catalyst which is selected from La₂O₃, Ag₂O and spinels.

2. A bifunctional air electrode according to claim 1 wherein the oxygen reduction catalyst is selected from MnO₂, KMnO₄, MnSO₄, SnO₂, Fe₂O₃, Co₃O₄, Co, CoO, Fe, Pt and Pd.

3. A bifunctional air electrode according to claim 1 wherein the bifunctional catalyst is La₂O₃.

4. A bifunctional air electrode according to claim 1 wherein the oxygen reduction catalyst is MnSO₄ and the bifunctional catalyst is La₂O₃.

5. A bifunctional air electrode according to claim 1 wherein the active layer comprises a hydrophobic binder and a pore former.

6. A bifunctional air electrode according to claim 5 wherein the hydrophobic binder is PTFE and/or wherein the pore former is selected from ammonium bicarbonate, high surface area carbon and graphite.

7. A bifunctional air electrode according to claim 1 wherein the oxygen evolution layer and the active layer comprise a single layer which has the combined properties of both layers.

8. A secondary battery comprising either a metal electrode or a metal hydride electrode, and an air electrode, wherein the air electrode is a bifunctional electrode comprising a gas diffusion layer, an active layer, an oxygen evolution layer and a current collector in electrical contact with the active layer;

wherein the active layer contains an oxygen reduction catalyst and a bifunctional catalyst.

9. A secondary battery according to claim 8 wherein the bifunctional catalyst is selected from La₂O₃, Ag₂O, Ag, perovskites and spinels.

10. A secondary battery according to claim 8 wherein the oxygen reduction catalyst is selected from MnO₂, KMnO₄, MnSO₄, SnO₂, Fe₂O₃, Co₃O₄, Co, CoO, Fe, Pt and Pd.

11. A secondary battery according to claim 8 wherein the bifunctional catalyst is La₂O₃.

12. A secondary battery according to claim 8 wherein the oxygen reduction catalyst is MnSO₄ and the bifunctional catalyst is La₂O₃.

13. A secondary metal-air battery according to claim 8 wherein the metal electrode comprise metal selected from Zn, Al, Mg, Fe, Li.

14. A secondary metal hydride-air battery according to claim 8 wherein the metal hydride electrode comprises a metal hydride selected from a group consisting of AB₅, AB₂, AB and A₂B, where A is an alkaline earth metal, transition metal, rare-earth metal, or actinide and B is a transition metal of the iron group.

15. A method for manufacturing a bifunctional air electrode comprising:

a) forming an active layer by;

(i) mixing a pore forming material, a binding material, an oxygen reduction catalyst and a bifunctional catalyst to produce an agglomerate;

(ii) adding an organic solvent to the dry agglomerate to produce a paste;

(iii) calendering the paste into a thin sheet to form an active layer;

b) forming a gas diffusion layer by;

(i) mixing a pore forming material and a binding material to produce an agglomerate;

(ii) adding an organic solvent to the dry agglomerate to produce a paste;

(iii) calendering the paste into a thin sheet to form a gas diffusion layer;

c) combining said active layer and said gas diffusion layer;

d) pressing a current collector into either of the layers to form the gas diffusion electrode.